1. Field of the Invention
The invention relates to concrete finishing trowels and, more particularly, relates to a walk-behind rotary concrete finishing trowel which is dynamically balanced to reduce operator effort. The invention additionally relates to a method of operating such a trowel.
2. Discussion of the Related Art
Walk behind trowels are generally known for the finishing of concrete surfaces. A walk behind trowel generally includes a rotor formed from a plurality of trowel blades that rest on the ground. The rotor is driven by a motor mounted on a frame or “cage” that overlies the rotor. The trowel is controlled by an operator via a handle extending several feet from the cage. The rotating trowel blades provide a very effective machine for finishing mid-size and large concrete slabs. However, walk behind trowels have some drawbacks.
For instance, the rotating blades impose substantial forces/torque on the cage that must be counteracted by the operator through the handle. Specifically, blade rotation imposes a torque on the cage and handle that tends to drive the handle to rotate counterclockwise or to the operator's right. In addition, blade rotation tends to push the entire machine linearly, principally backwards, requiring the operator to push forward on the handle to counteract those forces. The combined torque/forces endured by the operator are substantial and tend to increase with the dynamic coefficient of friction encountered by the rotating blades which, in turn, varies with the “wetness” of curing concrete. Counteracting these forces can be extremely fatiguing, particularly considering the fact that the machine is typically operated for several hours at a time.
The inventors investigated techniques for reducing the reaction forces/torque that must be endured by the operator. They theorized that these forces would be reduced if the trowel were better statically balanced than is now typically the case with walk behind trowels, in which the center of gravity is located slightly behind and to the left of the rotor's axis of rotation. The inventors therefore theorized that shifting the trowel's center of gravity forwardly would reduce reaction forces. However, they found that this shifting actually led to an increase in reaction forces generated during trowel operation.
The need therefore has arisen to provide a walk behind rotary trowel that requires substantially less operator effort to steer and control than conventional walk behind trowels.
The need additionally has arisen to reduce the operator effort required to steer and control a walk behind rotary trowel.